Understanding climate change as a knowledge controversy, this thesis provides new insights into the form, value and impact of the climate change debate on science and policy processes. Based on 99 interviews in New Zealand and the United Kingdom as well as social network analysis, it provides an original contribution to knowledge by identifying previously unknown sites of knowledge contestation within the climate change debate, in addition to contributory factors, and potential solutions to, debate polarisation. It also addresses a fundamental gap in the literature regarding the impact of controversy on the production of scientific knowledge and policy decision-making. This thesis comprises five standalone papers (Chapters 2-6) which together explore climate change as a knowledge controversy using frameworks from science and technology studies, sociology and geography. Chapter 2 finds that the most central blogs within the climate sceptical blogosphere predominantly focus on the scientific element of the climate debate. It argues that by acting as an alternative public site of expertise, the blogosphere may be playing a central role in perpetuating doubt regarding the scientific basis for climate change policymaking. Chapter 3 suggests that the binary and dualistic format of labels used within the climate debate such as “denier” or “alarmist” contribute towards polarisation by reducing possibilities for constructive dialogue. Chapter 4 investigates rationales for debate participation and argues that identifying and emphasising commonalities between previously polarised individuals may serve to reduce antagonism within the climate change debate. Chapter 5 investigates the impact of controversy on the production of scientific knowledge and finds that climate scientists identify substantial impacts on their agency as scientists, but not on scientific practice. It argues that this distinction indicates that boundarymaking may be understood as a more active and explicit process under conditions of controversy. Finally, Chapter 6 introduces the concept of post-decisional logics of inaction, emphasising the role of place in determining the influence of controversial knowledge claims on climate change policymaking. These findings make explicit the underlying politics of knowledge inherent within the climate change debate, and emphasise the need for a more attentive consideration of the role of knowledge, place and performativity in contested science and policy environments.